Carolina Songbird SE build

Attila

Right so Benji requested some gutshots of my Songbird, and I have let slip a few times on the forum that there was some kind of build going on

I know Its long over due, and as I had an opportunity to strip it down to put the new face plates on today ..... so what it is....

The Carolina Songbirds was conceived on the el34world.com website, as a team build lead by "Tubenit" so kudos to him.

Its a "D-style" pre-amp and tone circuit, which feeds a SE power amp circuit with a twist.

the pre-amp is a Dumble style, which lend itself to great clean chording and early overdrive and blooming notes when digging in with a pick. Finger picking is really tasty especially with a bucker, warm bluesy mmmmm mmmm

The twist is that I can run 1 x 6L6GC, or EL34 or 6V6 OR EL84 will be adding the option for 2 x 6V6 's in parallel soon

I am kinda nervous but here goes:

You can see the 3rd 9 pin base is wired differently which takes an EL84 in stead of the Octals - either or not both

The Cabinet was made by Paulo The-Wood-Guy who looked at me in disgust when I arrived with a box of nails and screws to help him.

We bought the wood thinking that is Red Elm when cleaned up it turns out to be Cherry wood.... I decided not to stain and
let nature take its course. Cherry darkens in 6-12 months very nicely.

The best part was I picked it up a less than pine ...way chuffed

I wanted to show as much wood as I can for now ........ I might put a grill cloth or the weaved rattan like the boogies

I have not bought speakers yet, still using the 70's "made for Stelphon" which seems to do the trick for now.

I just realized something, that the back bottom baffle is half the height it should be

Well that her ..... I will remake the faceplates in time ...

singemonkey

Very cool man.

TomCat

Looking nice......I agree those rear baffles look a little skimpy........ :-\ :-\

I'm gassing to start the build on my Marshall 18 Watter.......Only cash flow is holding me back at the moment...... ☹ ☹

AlanRatcliffe

Sounds pretty cool - I always like the amps where you can use a variety of o/p valves. Is the cab big or is the speaker smaller than 12"? I like the cast frame of the speaker - they don't often make 'em like that anymore.

Ummm... but "Middel"?

Attila

Ooops ... thats one reason why I must redo the plates

No its a big box I was struggling to find good 2 x 10's and Paulo went ahead and cut the hole for the 12" er

Whats the ratio on open backs one 1/3 or smaller 1/4 open ?

Norman86

very nice Attila! i like the natural look too! 8)

Attila

thanks Norm

Psean

Very cool! Interested to follow this one ?

Attila

thanks dudes

Karel-Mars

Attila Barath wrote: Whats the ratio on open backs one 1/3 or smaller 1/4 open ?

This is a tough question ??? But let's think about the purpose of the back panel.

Think of it like this. The front of the speaker is 180deg out of phase with the rear. So if your ear is equally distant from the front and the back, you'll hear nothing. So the back panel limits the rear reflections and accentuates the front sound.

Another thing. Imagine you have a piece of string. When your speaker is in it's cabinet, the distance from the front of the speaker to the rear of the speaker determines the amount of bass you hear. The longer the string needed, the more bass your speaker has. An infinite long string would be needed to reach around a infinite large baffle, that's why sealed cabinets are called infinite baffle speakers.

The other thing to consider is this. There are many paths from the front of the speaker to the rear. The shortest route determines the the whole bass response of the speaker. So if your speaker is mounted on the edge of you cabinet, the amount of bass would be determined by the path length round the closest side panel. So that is why you see on rectangular cabinets, only back panels at the top and the bottom of the cabinet. It increase the path length from the front to the rear around the narrow section of the cabinet.

But more bass is not necessarily better. It takes more energy to amplify bass, so the more bass you cabinet can deliver, the less loud it sounds relatively. So if you want to cut through the noise, you need to limit your bass response.

Other aspects of the rear baffle size are determined by the limitations of the driver's design. All speakers have a limited distance it can move on the X axis. To stop your driver from jumping out of the magnets groove, you need to dampen the movement when it gets to extremes. This is why closed speakers are great for loud playing.

Then speaker drivers have resonance. It is the frequency it plays the easiest. On the Celestions it is about 70Herz. If you do not want bass boominess and the associated lack of power, you need to bring some out-of-phase sound from the rear to the front to cancel the resonance so you sound is equally loud on all frequencies :bopping:

Look at the VOX rear panel. Think of the speaker as a piston pushing air. The effective area on top of the speaker that pushes the air is a figure to keep in mind. A good starting point is to make the gap in the rear panel as large as the piston area of the speaker. The AC30 has two 12" and the gap is about the the double the size of the Celestion's effective piston area ?

Attila

Thanks Karel

So I guess the answer is 5 !!! :?

The cab was based on a Trinity Cab 15 with the intention to place 2x10' speakers but ended up a 1x12. except Paulo the wood guy ran skimp in his wood estimations and was short hence the deviation from the cutting plan ( missing approx 100mm on the rear baffle)

I follow what you mean, and the variables associated thereto. I was hopping for a simple "rule-of-thumb' answer.

But you've given me direction on how to go about answering that question, the crux is that there are too many variables to have a 1 size fits all

Many thanks thanks for your input.

aja

Karel wrote:
Attila Barath wrote: Whats the ratio on open backs one 1/3 or smaller 1/4 open ?
that's why sealed cabinets are called infinite baffle speakers.

~~You know infinitely more than me about these things, but I thought this is what an infinite baffle means? ie totally separate front and rear?~~

Bah! whatever... Interesting stuff below nonetheless...

Lots of links:

http://ibsubwoofers.proboards.com/index.cgi?board=general

Explanation:

http://home.comcast.net/~infinitelybaffled/index.html

Build pics:

http://www.hometheatershack.com/forums/ib-infinite-baffle-subwoofer-build-projects/6431-finished-ib-projects-photos.html

Some good stuff here:

http://home.comcast.net/~thomasw-2/SubwooferSetupandEQpage.html

shaunf

Very nice looking amp Attila!

Very interesting post too, Karel. Thanks for sharing.

Nicholas-L

Looks awesome man. ?

TomCat

Looks like the O/P tranny worked out well......

Attila

It did "nudge nudge wink wink" :? thanks to you

Manfred-Klose

i request some sound samples or a youtube video ?

Attila

Ok Will put something together as soon as